The prior art accepts free piston internal combustion engines operating on both the Otto cycle and Diesel cycle principle, the former being constant volume and the latter being constant pressure, in theory. It is the latter constant pressure concept with which this invention is concerned; with engines that compress the full cylinder volume and inject fuel during piston travel. At the present state of the art compression ignition engines, Diesels, are acknowledged to compress 40% excess air in order to establish auto ignition temperature, and although this has its benefits in providing more than adequate support for combustion, it has great disadvantages in the waste of energy provided for the compressive function and in the increased structural requirements of large volume high compression engines; and all of which involves inefficiency which entails friction and heat losses. Therefore, it is an object of this invention to provide a free piston heat engine wherein a substantial portion of the compression is restricted to low pressure for support of combustion, wherein a limited portion of the compression is extended to high pressure for establishing auto ignition, and wherein combustion gases are extracted for delivering power in the form of heat and/or torque. With the concept herein disclosed, the aforementioned 40% excess air is reduced to a minumum and/or to a small excess, say for example 10% to 15% or less as may be desired; and combustion gases are by-passed to an impulse turbine during the piston power stroke, sufficient to drive a scavenger blower and to provide a torque drive as circumstances require.
The engine of the present invention is a departure from both the Otto cycle and Diesel cycle concepts in that full volume compression and measured fuel injection at the beginning of the power stroke are avoided. Replacing the foregoing is controlled injection as it is disclosed in my U.S. Pat. No. 4,070,998 entitled Compression Ignition Controlled Pressure Heat Engine, issued Jan. 31, 1978. To this end it is an object of this invention to continuously inject fuel in a free piston engine throughout the effective portion of the work stroke, at a controlled rate establishing burning pressures less than the pressure of the aforementioned storage air that is thereby releasable from the aforementioned storage member to support combustion within the cylinder.
An object of this invention is to advantageously employ the constant volume variable potency injectors as disclosed in U.S. Pat. Nos. 3,749,097 and 3,921,599 issued to me on July 31, 1973 and Nov. 25, 1975 respectively. It is by means of these fuel injectors, or like injectors, that controlled fuel burning and cylinder pressures are maintained below the stored combustion supporting air pressures. With this invention a constant volume pump intermixes two liquids and discriminately injects the admixture thereof discretely therefrom and into the engine cylinder at a controlled potency. The injector per se is characterized by its differential pump means which are advantageously employed to acquire structural strength and accurately metered fuel injection.